The invention relates to a method and apparatus for screenless treatment of fiber material, such as digesting of fiber material in a continuous digester, and to a means and method for preventing the channeling of fiber material treating liquid in a continuous digester or the like. Screenless treatment of fiber material per se has been disclosed in U.S. patent application Ser. Nos. 423,812, filed Dec. 11, 1973 abandoned; 592,659, filed July 2, 1975 U.S. Pat. No. 4,028,171; 613,554, filed Sept. 15, 1975 abandoned; and 659,638, filed Feb. 20, 1976 U.S. Pat. No. 4,061,193, and while such fiber material treatment is generally successful, sometimes problems can arise with respect to the treatment liquid forming channels in flowing through the fiber material, and going directly to the outlet without evenly and uniformly treating and/or heating the fiber material. According to the present invention, channeling of liquid through the fiber material column has been substantially eliminated while screenless treatment is still practiced.
According to the present invention, apparatus for the treatment of cellulose fiber material is provided, including an inner vertically extending vessel having a diameter D, and an outer vertically extending vessel having a diameter E (wherein E is larger than D). A bottom portion of the inner vessel extends into the outer vessel and defines an annular space in the outer vessel between the inner vessel and the outer vessel. Means for introducing fiber material treating liquid into a column of fiber material in the outer vessel is provided, such as a pipe extending into the outer vessel a distance J wherein J is 1/2E, and means (including a pump) are provided for withdrawing liquid introduced into the column in the outer vessel from the annular space to an area remote from the vessels. The means for preventing channeling of liquid through the column include at least three vertically extending baffles disposed in the annular space and partitioning it into at least three distinct flow areas, an outlet nozzle associated with each flow area, and means for operatively connecting each of the outlet nozzles to the liquid withdrawing means. Also, means are provided for backflushing one of the flow areas while withdrawal of liquid takes place through the other areas to clean the flow area of material and to insure future no-channeling flow therethrough, and the flow area that is backflushed is continuously changed.
Also, according to the present invention, a method for treating cellulose fiber material is provided utilizing an inner vertically extending vessel having a diameter D and an outer vertically extending vessel having a diameter E greater than D, and a bottom portion of the inner vessel extending into the outer vessel and defining an annular space in the outer vessel between the inner vessel and the outer vessel. According to the method of the invention, cellulose fiber material is passed through the inner vessel into the outer vessel to establish a column of cellulose fiber material extending downwardly from the bottom portion of the inner vessel. Cellulose fiber treating liquid, such as digesting liquor, is introduced into the material column. At least three distinct flow areas of fiber material treating liquid through the fiber column to the annular space are established, at least two of the three distinct flow areas having liquid flowing therethrough from the column through the annular space so that channeling of liquid flow through the column does not take place. Liquid is withdrawn from the annular space in the outer vessel at a rate relative to the dimensions of the vessel such that a stilling well effect is created in the annular space and fiber material from the column is not entrained in liquid flow in the annular space, and so that no screening of the liquid flow is necessary. Liquid is forced back into the annular space through one of the flow areas while the withdrawal of liquid takes place through at least two flow areas, and the flow area that liquid is forced back into is continuously switched.
It is the primary object of the present invention to provide a method of and apparatus for the screenless treatment of cellulose fiber material without channeling of treatment liquid. This and other objects of the invention will become clear from an inspection of the detailed description of the invention, and from the appended claims.